Environmentally acceptable well cement fluid loss control additives, compositions, and methods

ABSTRACT

Environmentally acceptable well cement fluid loss control additives, cement compositions including the additives and methods of using the compositions are provided. The environmentally acceptable fluid loss control additives are comprised of ethoxylated hydroxyethylcellulose having a reduced molecular weight.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 09/732,861 filed on Dec. 8,2000, now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to subterranean well cementing operations,and more particularly, to environmentally acceptable well cement fluidloss control additives, well cement compositions containing theadditives and methods of using the compositions.

2. Description of the Prior Art

Hydraulic cement compositions are commonly utilized in subterranean wellcompletion and remedial operations. For example, hydraulic cementcompositions are used in primary cementing operations whereby strings ofpipe such as casings and liners are cemented in well bores. Inperforming primary cementing, a hydraulic cement composition is pumpedinto the annular space between the walls of a well bore and the exteriorsurfaces of a pipe string disposed therein. The cement composition ispermitted to set in the annular space thereby forming an annular sheathof hardened substantially impermeable cement therein which supports andpositions the pipe string in the well bore and bonds the exteriorsurfaces of the pipe string to the walls of the well bore. Hydrauliccement compositions are also utilized in remedial cementing operationssuch as plugging highly permeable zones or fractures in well bores,plugging cracks or holes in pipe strings and the like.

Fluid loss control agents are used in well cement compositions to reducefluid loss from the cement compositions to the permeable formations orzones into or through which the cement compositions are pumped. Inprimary cementing, the loss of fluid, i.e., water, from the cementcompositions to a permeable subterranean formation or zone can result inpremature gelation of the cement composition whereby bridging of theannular space between the permeable formation or zone and the pipestring being cemented prevents the cement composition from being placedover the entire length of the annulus.

Heretofore, environmentally acceptable hydroxyethylcellulose having anaverage molecular weight of about 90,000 and higher has been utilized asa well cement composition fluid loss control agent. However, the use ofsuch hydroxyethylcellulose as a cement composition fluid loss additivehas involved a number of disadvantages. For example, the ability of thehydroxyethylcellulose to prevent fluid loss in a cement compositiondecreases rapidly at temperatures above about 230° F. In addition, thehydroxyethylcellulose has a limited salt tolerance. That is, if the saltcontent of the water in the cement composition is above about 5% byweight of the water, the ability of the hydroxyethylcellulose to preventfluid loss is reduced. In offshore cementing operations, thehydroxyethylcellulose has been utilized in an aqueous solution so thatit can be readily added to the mix water or the cement slurry. In orderto prevent the aqueous solution of the hydroxyethylcellulose from havingtoo high a viscosity, the hydroxyethylcellulose must be dissolved inrelatively large quantities of water making its mixing and handling moredifficult than other fluid loss control agents.

Thus, there is a need for an improved environmentally acceptablehydroxyethylcellulose fluid loss control agent which can be utilized attemperatures higher than 230° F., which can be dissolved in relativelysmall quantities of water without greatly increasing the viscosity ofthe solution and which has a higher salt tolerance while maintaining thesame fluid loss control.

SUMMARY OF THE INVENTION

The present invention provides environmentally acceptable well cementfluid loss control additives, well cement compositions and methods ofusing the compositions which meet the needs described above and overcomethe deficiencies of the prior art. The environmentally acceptable wellcement fluid loss control additives of this invention are basicallycomprised of hydroxyethylcellulose having a reduced average molecularweight of about 60,000 ethoxylated in an amount in the range of fromabout 1 to about 4 moles of ethylene oxide per anhydroglucose unit,i.e., an average molecular substitution of ethylene oxide of 2.5 peranhydroglucose unit. The fluid loss additives can also include atemperature stability increasing agent to increase the temperature atwhich the additives remain stable and continue to prevent fluid loss.The temperature stability increasing agent can be selected fromsynthetic hectorite, magnesium oxide and sodium thiosulfate. Of these,magnesium oxide is preferred.

The improved well cement compositions of this invention are basicallycomprised of a hydraulic cement, water present in an amount sufficientto form a pumpable slurry and the environmentally acceptable well cementfluid loss control additive of this invention, i.e.,hydroxyethylcellulose having a reduced average molecular weight of about60,000 ethoxylated in an amount in the range of from about 1 to about 4moles of ethylene oxide per anhydroglucose unit. The fluid loss controladditive can also include a temperature stability increasing agentselected from the group of synthetic hectorite, magnesium oxide andsodium thiosulfate. Synthetic hectorite and sodium thiosulfate can beadded in particulate solid form directly to the hydraulic cement or mixwater utilized, or it can be dissolved in water whereby a storableaqueous solution results which can be readily combined with the mixwater or cement slurry. Magnesium oxide can only be added to the mixwater of the cement slurry.

The methods of this invention for cementing a zone in a subterraneanformation penetrated by a well bore are basically comprised of the stepsof preparing a cement composition of this invention including the abovedescribed environmentally acceptable well cement fluid loss controladditive, placing the cement composition in the zone to be cemented andallowing the cement composition to set into an impermeable solid masstherein.

It is, therefore, a general object of the present invention to provideimproved environmentally acceptable well cement fluid loss controladditives, improved well cement compositions including the additives andmethods of using the cement compositions.

Other and further objects, features and advantages of the presentinvention will be readily apparent to those skilled in the art upon areading of the description of preferred embodiments which follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

As mentioned, the environmentally acceptable well cement fluid losscontrol additive of this invention is basically comprised ofhydroxyethylcellulose having a reduced molecular weight in the range offrom about 30,000 to about 90,000, i.e., an average molecular weight ofabout 60,000, ethoxylated in an amount in the range of from about 1 toabout 4 moles of ethylene oxide per anhydroglucose unit, i.e., anaverage molecular substitution in the range of from about 2.2 to about2.7 per anhydroglucose unit, most preferably 2.5 per anhydroglucoseunit. The average molecular weight of commercially availablehydroxyethylcellulose is about 90,000 or higher. While suchhydroxyethylcellulose can be and has been utilized in well cementcompositions as an environmentally acceptable well cement fluid losscontrol additive, it suffers from the disadvantages that it is unstableand its fluid loss control properties are significantly reduced attemperatures above about 230° F. and/or when it is in contact with saltwater containing salt in an amount above about 5% by weight of thewater. In addition, when the commercially availablehydroxyethylcellulose is dissolved in water so that it can be added to acement slurry or its mix water as a liquid, the resulting solution has ahigh viscosity. As a result, a liquid hydroxyethylcellulose solutioncontaining only about 7.5% by weight commercial hydroxyethylcellulosecan be used.

The above is contrasted with the ethoxylated hydroxyethylcellulose ofreduced molecular weight of the present invention which is stable andeffectively controls fluid loss from cement compositions at temperaturesabove 230° F. to at least about 260° F., can be utilized in contact withsalt water containing salt up to 37.2% by weight without losingeffectiveness and can be dissolved in water up to about 12.5% by weightof the resulting solution which remains relatively low in viscosity.

In order to improve the temperature stability of the improvedethoxylated hydroxyethylcellulose fluid loss control additive of thisinvention, a temperature stability increasing agent can be combined withthe ethoxylated hydroxyethylcellulose. Suitable temperature stabilityincreasing agents which can be utilized include, but are not limited to,synthetic hectorite, magnesium oxide and sodium thiosulfate. Of these,magnesium oxide is preferred. When used, the temperature stabilityincreasing agent is combined with the ethoxylated hydroxyethylcellulosein an amount in the range of from about 50% to about 500% by weight ofthe ethoxylated hydroxyethylcellulose, preferably in an amount of about100%.

The improved environmentally acceptable ethoxylatedhydroxyethylcellulose fluid loss control additive of this invention canbe prepared by treating a commercially available hydroxyethylcellulosehaving an average molecular weight of about 90,000 or higher withhydrogen peroxide using known techniques and amounts. That is, thecommercially available hydroxyethylcellulose is slurried in a mixture ofacetone and water and hydrogen peroxide is added to the slurry in anamount and under conditions such that the molecular weight of thehydroxyethylcellulose is reduced to in the range of from about 30,000 toabout 90,000, i.e., an average molecular weight of about 60,000. Thereduced molecular weight hydroxyethylcellulose formed is separated fromthe reaction mixture purified, dried and ground.

A preferred environmentally acceptable fluid loss control additive ofthis invention is comprised of hydroxyethylcellulose having a reducedmolecular weight in the range of from about 30,000 to about 90,000ethoxylated in an amount in the range of from about 1 to about 4 molesof ethylene oxide per anhydroglucose unit.

Another preferred environmentally acceptable fluid loss control additiveof this invention is comprised of hydroxyethylcellulose having a reducedaverage molecular weight of about 60,000 ethoxylated in an averageamount of about 2.5 moles of ethylene oxide per anhydroglucose unit.

Yet another preferred fluid loss control additive of this invention iscomprised of hydroxyethylcellulose having a reduced molecular weight inthe range of from about 30,000 to about 90,000 ethoxylated in an amountin the range of from about 1 to about 4 moles of ethylene oxide peranhydroglucose unit and having a temperature stability increasing agentselected from the group consisting of synthetic hectorite, magnesiumoxide and sodium thiosulfate combined therewith in an amount in therange of from about 50% to about 500% by weight of the ethoxylatedhydroxyethylcellulose.

Still another preferred fluid loss control additive of this invention iscomprised of hydroxyethylcellulose having a reduced average molecularweight of about 60,000 ethoxylated in an average amount of about 2.5moles of ethylene oxide per anhydroglucose unit and having a temperaturestability increasing agent comprised of magnesium oxide combinedtherewith in an amount of about 100% by weight of the ethoxylatedhydroxyethylcellulose.

The improved well cement compositions of the present invention arebasically comprised of a hydraulic cement, sufficient water to form apumpable slurry and the environmentally acceptable well cement fluidloss control additive described above.

A variety of hydraulic cements can be utilized in accordance with thepresent invention including those comprised of calcium, aluminum,silicon, oxygen and/or sulfur which set and harden by reaction withwater. Such hydraulic cements include, but are not limited to, Portlandcements, pozzolana cements, gypsum cements, high alumina contentcements, silica cements and high alkalinity cements. Portland cementsare generally preferred for use in accordance with the presentinvention, and Portland cements of the types defined and described inAPI Specification For Materials And Testing For Well Cements, APISpecification 10, Fifth Edition, dated Jul. 1, 1990 of the AmericanPetroleum Institute are particularly preferred. API Portland cementsinclude classes A. B, C, G and H. API classes G and H are preferred withclass G being the most preferred.

The water utilized in the compositions of this invention can be freshwater, salt water, i.e., water containing one or more salts dissolvedtherein, brine, i.e., saturated salt water produced from subterraneanformations, or seawater. Generally, the water can be from any sourceprovided it does not contain an excess of compounds that adverselyaffect other components in the cement compositions. The water is presentin a cement composition of this invention in an amount sufficient toform a pumpable slurry. More particularly, the water is present in acement composition of this invention in an amount in the range of fromabout 25% to about 100% by weight of hydraulic cement therein, morepreferably in an amount of about 44%.

An environmentally acceptable well cement fluid loss control additive ofthis invention described above is included in a cement composition ofthis invention in an amount in the range of from about 0.1% to about 2%by weight of cement in the composition. As mentioned, the additive canbe comprised of an ethoxylated hydroxyethylcellulose having a reducedmolecular weight or it can be comprised of the ethoxylatedhydroxyethylcellulose of a reduced molecular weight combined with atemperature stability increasing agent. The additive can be mixed inparticulate solid form with the hydraulic cement or mixing water priorto mixing the cement composition or it can be dissolved in water to forma storable liquid additive which can readily be added to the mixingwater or to the cement slurry after it is formed.

A preferred cement composition of this invention is comprised of ahydraulic cement, water present in an amount sufficient to form apumpable slurry and an environmentally acceptable fluid loss controladditive comprised of hydroxyethylcellulose having a reduced averagemolecular weight of about 60,000 ethoxylated with an average amount ofabout 2.5 moles of ethylene oxide per anhydroglucose unit, the fluidloss control additive being present in the composition in an amount ofabout 0.75% by weight of cement in the composition.

Another preferred cement composition of this invention is comprised ofhydraulic cement, water present in an amount sufficient to form apumpable slurry and an environmentally acceptable fluid loss controladditive comprised of hydroxyethylcellulose having a reduced molecularweight in the range of from about 30,000 to about 90,000 ethoxylated inan amount in the range of from about 1 to about 4 moles of ethyleneoxide per anhydroglucose unit, the fluid loss control additive beingpresent in the composition in an amount in the range of from about 0.1%to about 2% by weight of cement in the composition.

Yet another preferred composition of this invention is comprised of ahydraulic cement, water present in an amount sufficient to form apumpable slurry and an environmentally acceptable fluid loss controladditive comprised of hydroxyethylcellulose having a reduced averagemolecular weight of about 60,000 ethoxylated in an average amount in therange of from about 2.2 to about 2.7 moles of ethylene oxide peranhydroglucose unit combined with a temperature stability increasingagent selected from the group consisting of synthetic hectorite,magnesium oxide and sodium thiosulfate, the temperature stabilityincreasing agent being present in the additive in an amount in the rangeof from about 50% to about 500% by weight of the ethoxylatedhydroxyethylcellulose and the additive being present in the cementcomposition in an amount in the range of from about 0.1% to about 2% byweight of cement in the composition.

Still another preferred composition of this invention is comprised ofhydraulic cement, sufficient water to form a pumpable slurry and anenvironmentally acceptable fluid loss control additive comprised ofhydroxyethylcellulose having a reduced average molecular weight of about60,000 ethoxylated in an average amount of about 2.5 moles of ethyleneoxide per anhydroglucose unit combined with a temperature stabilityincreasing agent comprised of magnesium oxide, the temperature stabilityincreasing agent being present in an amount of about 100% by weight ofthe ethoxylated hydroxyethylcellulose and the fluid loss controladditive being present in the cement composition in an amount of about0.75% by weight of cement in the composition.

As will be understood by those skilled in the art, the well cementcompositions of this invention can include other conventional wellcement additives such as set accelerators, set retarding agents,fillers, weighting materials and the like.

The environmentally acceptable fluid loss control additives of thisinvention are of low cost as compared to synthetic fluid loss controladditives, they function to prevent fluid loss at temperatures of 280°F. and higher, they remain stable in the presence of salt water and theycan be dissolved in water to form storable liquid additives insufficient amounts without increasing the viscosities of the resultingadditive solutions or increasing the viscosities of the cementcompositions in which they are utilized to unacceptable levels.

The methods of the present invention for cementing a subterranean zonepenetrated by a well bore are basically comprised of the steps ofpreparing a cement composition of this invention as described above,placing the cement composition in the zone to be cemented and allowingthe cement composition to set into an impermeable solid mass therein.

In order to further illustrate the environmentally acceptable wellcement fluid loss control additives, well cement compositions andmethods of this invention, the following examples are given.

EXAMPLE 1

A cement composition including a commercially availablehydroxyethylcellulose fluid loss control additive having an averagemolecular weight of about 90,000 and other conventional additives wasprepared. Various additional cement compositions which included a fluidloss control additive of the present invention and the same otherconventional additives were also prepared. The composition including theconventional fluid loss control additive was tested at a temperature of230° F. and the compositions containing the fluid loss control additiveof the present invention were tested at 250° F. and 260° F. forthickening time, rheology, free water, settling, and stirring fluidloss. The results of these tests are set forth in Table I below.

The thickening time, rheology, free water and settling tests were allconducted in accordance with the procedures set forth in the abovementioned API Specification 10. The stirring fluid loss and BP-settlingtests were performed in accordance with standard test procedures setforth in the Halliburton Global Standard Manual dated May 1997. Thespecific gravity top-bottom test is conducted by taking four 10 cubiccentimeter samples from the cement slurry utilized in the free watertest. The specific gravities of the samples are then determined and ifthere is a large difference between the top and bottom specificgravities, instability is indicated.

The results of these tests are given in Table I below.

TABLE I Fluid Loss And Other Tests TEST CEMENT COMPOSITION COMPONENTSNo. 1 No. 2 No. 3 No. 4 Cement, API Class G, parts by weight 100 100 100100 Fresh Water, parts by weight 46 46 46 46 Prior Art Fluid LossControl Additive¹, parts by weight 1 — — — Fluid Loss Control Additive²of the present invention, parts by weight — 1.5 1.75 1.75 ManganeseTetroxide³, parts by weight 20 20 20 20 Silica Fume⁴, parts by weight 55 5 5 Copolymer of 2-acrylamido-2-methylpropane sulfonic acid and malicacid⁵, parts by weight 0.6 0.7 0.8 1 Silica Flour⁶, parts by weight 3535 35 35 DENSITY, lb/gal 17.5 17.5 17.5 17.5 THICKENING TIME Temperature230° F. 250° F. 250° F. 260° F. 70 Bc, hrs:mins. 4:45 3:02 3:22 4:21 100Bc, hrs:mins. 4:50 3:05 3:27 4:27 RHEOLOGY AFTER CONDITIONINGTemperature 230° F. 250° F. 250° F. 260° F. 300-200-100 160-102-48182-124-65 210-165-102 200-175-94 60-30-6-3 28-13-4-3 40-20-5-363-43-9-5 58-29-7-5 FREE WATER. % by volume 0 0 0 0 SETTLING, % byvolume 0 0 0 0 SPECIFIC GRAVITY, top/bottom 2.10/2.15 2.10/2.102.09/2.08 — STIRRING FLUID LOSS Temperature 230° F. 250° F. 250° F. 260°F. cc/30 min. 130 56 19 63 BP - Settling Deviation, % 2 2 2 2 HeightReduction, mm 2 2 3 2 Specific gravity from Top-Bottom 2.07 2.09 2.082.07 1 2.09 2.10 2.08 2.08 2 2.09 2.11 2.09 2.08 3 2.10 2.12 2.11 2.08 42.12 2.14 2.13 2.11 ¹Hydroxyethylcellulose having an average molecularweight of 90,000. ²Hydroxyethylcellulose having an average molecularweight of 60,000 ethoxylated with 2.5 moles of ethylene oxide peranhydroglucose unit. ³Weighting agent. ⁴Anti-free water additive. ⁵Setretarding additive. ⁶Anti-strength retrogression additive.

From Table I it can be seen that the fluid loss control additive of thepresent invention is effective up to a temperature of at least 260° F.

EXAMPLE 2

Additional test cement slurries were prepared as described in Example 1except that the ethoxylated hydroxyethylcellulose fluid loss controladditive of the present invention included synthetic hectorite and thetests were conducted at temperatures of 230° F., 260° F., 275° F. and300° F. The test cement compositions were tested in the same manner asdescribed in Example 1. The results of these tests are given in Table IIbelow.

TABLE II Fluid Loss And Other Tests TEST CEMENT COMPOSITION COMPONENTSNo. 1 No. 2 No. 3 No. 4 Cement, API Class G, parts by weight 100 100 100100 Fresh Water, parts by weight 46 46 46 46 Prior Art Fluid LossControl Additive¹, parts by weight 1.75 — — — Fluid Loss ControlAdditive² of the present invention, parts by weight — 1.3 1.3 1.3Manganese Tetroxide³, parts by weight 20 20 20 20 Silica Fume⁴, parts byweight 5 5 5 5 Copolymer of 2-acrylamido-2-methylpropane sulfonic acidand malic acid⁵, parts by weight 0.6 1 1.2 1.2 Silica Flour⁶, parts byweight 35 35 35 35 DENSITY, lb/gal 17.5 17.5 17.5 17.5 THICKENING TIMETemperature 230° F. 260° F. 275° F. 300° F. 70 Bc, hrs:mins. 4:45 4:204:38 — 100 Bc, hrs:mins. 4:50 4:26 4:40 — RHEOLOGY AFTER CONDITIONINGTemperature 230° F. 260° F. 275° F. 300° F. 300-200-100 160-102-48275-207-160 225-150-75 225-150-75 60-30-6-3 28-13-4-3 100-60-10-545-22-4-2 45-22-4-2 FREE WATER. % by volume 0 0 0 0 SETTLING, % byvolume 0 0 0 0 SPECIFIC GRAVITY, top/bottom 2.10/2.15 2.10/2.152.08/2.12 2.06/2.12 STIRRING FLUID LOSS Temperature 230° F. 260° F. 275°F. 300° F. cc/30 min. 130 24 40 50 BP - Settling Deviation, % 2 1 2 —Height Reduction, mm 2 2 2 — Specific gravity from Top-Bottom 2.07 2.182.08 — 1 2.09 2.18 2.09 — 2 2.09 2.18 2.10 — 3 2.10 1.29 2.10 — 4 2.122.20 2.13 — ¹Hydroxyethylcellulose having an average molecular weight of90,000. ²Hydroxyethylcellulose having a molecular weight of 60,000ethoxylated with 2.5 moles of ethylene oxide per anhydroglucose unitcombined with synthetic hectorite whereby the synthetic hectorite waspresent in an amount of 12% by weight of the mixture. ³Weighting agent.⁴Anti-free water additive. ⁵Set retarding additive. ⁶Anti-strengthretrogression additive.

From Table II it can be seen that the fluid loss control additive ofthis invention including synthetic hectorite had increased temperaturestability.

EXAMPLE 3

The procedure set forth in Example 2 was repeated except that the cementcomposition including the commercially available fluid loss controladditive was not tested and the fluid loss control additive of thepresent invention included magnesium oxide. Also, the tests wereconducted at 230° F., 250° F., 260° F. and 280° F. The test cementcompositions were tested in the same manner as described in Example 1except the BP-settling test was not conducted. The results of thesetests are given in Table III below.

TABLE III Fluid Loss And Other Tests TEST CEMENT COMPOSITION COMPONENTSNo. 1 No. 2 No. 3 No. 4 Cement, API Class G, parts by weight 100 100 100100 Fresh Water, parts by weight 50 50 50 50 Fluid Loss ControlAdditive¹ of the present invention, parts by weight 1.25 1.25 1.25 1.25Manganese Tetroxide², parts by weight 20 20 20 20 Silica Fume³, parts byweight 5 5 5 5 Copolymer of 2-acrylamido-2-methylpropane sulfonic acidand malic acid⁴, parts by weight 0.8 0.8 0.8 1.0 Silica Flour⁵, parts byweight 35 35 35 35 DENSITY, lb/gal 17 17 17 17 RHEOLOGY AT MIX300-200-100 289-205-110 300+-210-115 — 300+−265-225 60-30-6-3 68-36-8-471-37-8-4 — 152-83-20-11 RHEOLOGY AFTER CONDITIONING Temperature 195° F.195° F. — 195° F. 300-200-100 95-60-23 105-71-35 — 230-151-77 60-30-6-316-7-2-1 21-10-2-1 — 46-22-4-2 FREE WATER. % by volume 0 0 — 0 SETTLING,% by volume 0 — — 0 SPECIFIC GRAVITY, top/bottom 1.982/2.093 — —2.027/2.082 STIRRING FLUID LOSS Temperature 250° F. 250° F. 260° F. 280°F. cc/30 min. 1^(st) Test 2^(nd) Test 1^(st) Test 2^(nd) Test 100 116 3260 77 84 ¹Hydroxyethylcellulose having a molecular weight of 60,000ethoxylated with 2.5 moles of ethylene oxide per anhydroglucose unitcombined with magnesium oxide whereby the magnesium oxide was present inan amount of 50-100% by weight of the mixture. ²Weighting agent.³Anti-free water additive. ⁴Set retarding additive. ⁵Anti-strengthretrogression additive.

From Table III it can be seen that the magnesium oxide in the fluid losscontrol additive increased the temperature at which the fluid losscontrol additive remains stable.

Thus, the present invention is well adapted to carry out the objects andattain the ends and advantages mentioned as well as those which areinherent therein. While numerous changes may be made by those skilled inthe art, such changes are encompassed within the spirit of thisinvention as defined by the appended claims.

What is claimed is:
 1. A cement composition comprising: a hydrauliccement; water present in an amount sufficient to form a pumpable slurry;and an environmentally acceptable fluid loss control additive comprisinghydroxyethylcellulose having a reduced molecular weight in the range offrom about 30,000 to about 90,000 ethoxylated in an amount in the rangeof from about 1 to about 4 moles of ethylene oxide per anhydroglucoseunit.
 2. The composition of claim 1 wherein said hydraulic cement isPortland cement.
 3. The composition of claim 1 wherein said hydrauliccement is Portland API Class G cement.
 4. The composition of claim 1wherein said water is fresh water or salt water.
 5. The composition ofclaim 1 wherein said water is present in an amount in the range of fromabout 25% to about 100% by weight of cement in said composition.
 6. Thecomposition of claim 1 wherein said hydroxyethylcellulose has an averagemolecular weight of about 60,000.
 7. The composition of claim 1 whereinsaid hydroxyethylcellulose is ethoxylated in the range of from about 2.2to about 2.7 moles of ethylene oxide per anhydroglucose unit.
 8. Thecomposition of claim 1 wherein said hydroxyethylcellulose is ethoxylatedin an average amount of about 2.5 moles of ethylene oxide peranhydroglucose unit.
 9. The composition of claim 1 wherein the additiveis stable and effectively controls fluid loss from cement compositionsat temperatures above 230° F. to at least about 260° F.
 10. Thecomposition of claim 1 wherein the additive can be utilized in contactwith salt water containing salt up to 37.2% by weight without losingeffectiveness.
 11. The composition of claim 1 wherein the additive canbe dissolved in water up to about 12.5% by weight of the resultingsolution.
 12. The composition of claim 1 further comprising atemperature stability increasing agent.
 13. The composition of claim 12wherein said temperature stability increasing agent is selected from thegroup consisting of synthetic hectorite, magnesium oxide and sodiumthiosulfate.
 14. The composition of claim 12 wherein said temperaturestability increasing agent is magnesium oxide.
 15. The composition ofclaim 12 wherein said temperature stability increasing agent is presentin said additive in an amount in the range of from about 50% to about500% by weight of said ethoxylated hydroxyethylcellulose.
 16. Thecomposition of claim 12 wherein said temperature stability increasingagent is present in an amount of about 100% by weight of saidethoxylated hydroxyethylcellulose.
 17. A cement composition comprising:a hydraulic cement; water present in an amount sufficient to form apumpable slurry; an improved environmentally acceptable well cementfluid loss control additive comprising hydroxyethylcellulose having areduced molecular weight in the range of from about 30,000 to about90,000 and being ethoxylated in an amount in the range of from about 1to about 4 moles of ethylene oxide per anhydroglucose unit; and atemperature stability increasing agent present in said additive in anamount in the range of from about 50% to about 500% by weight of saidethoxylated hydroxyethylcellulose and selected from the group consistingof synthetic hectorite, magnesium oxide and sodium thiosulfate.
 18. Thecomposition of claim 17 wherein said hydroxyethylcellulose has anaverage molecular weight of about 60,000.
 19. The composition of claim17 wherein said hydroxyethylcellulose is ethoxylated in an averageamount of about 2.5 moles of ethylene oxide per anhydroglucose unit. 20.The composition of claim 17 wherein said temperature stabilityincreasing agent is magnesium oxide.
 21. The composition of claim 17wherein said temperature stability increasing agent is present in anamount of about 100% by weight of said ethoxylatedhydroxyethylcellulose.
 22. A cement composition comprising: a hydrauliccement; water present in an amount sufficient to form a pumpable slurry;an improved environmentally acceptable well cement fluid loss controladditive comprising hydroxyethylcellulose having a reduced molecularweight of about 60,000 and being ethoxylated in an amount in the rangeof from about 2.5 moles of ethylene oxide per anhydroglucose unit; and atemperature stability increasing agent present in said additive in anamount of about 100% by weight of said ethoxylated hydroxyethylcelluloseand wherein said temperature stability increasing agent is magnesiumoxide.